Nocturnal enuresis (NE) or bedwetting is a common condition, occurring in about one in 10 children aged 7 years. It is important to differentiate between primary monosymptomatic nocturnal enuresis (PMNE) and nocturnal enuresis with associated daytime symptoms.
If nocturnal enuresis is an isolated symptom with no other symptoms to suggest bladder dysfunction, and the child has not been dry at night for more than 6 months, it is termed PMNE. Daytime symptoms may be subtle and include frequency, urgency, or occasional daytime wetting.
Bedwetting is caused by several factors, either in isolation or in combination. There may be a strong family history. If one parent was affected, up to 45% of children may have NE, and this rises to 77% if both parents were affected.
Normally, distension of the bladder to capacity should wake the child to void, but in NE the child is usually a deep sleeper and does not react to this stimulus. An overactive bladder may cause daytime symptoms, but the symptoms are more pronounced at night due to lack of the arousal reflex.
The overactive bladder may lead to a functionally small capacity bladder, with an inability to hold normal amounts of nocturnal urine production. Urine production is less at night time, but in NE may be greater than normal. Stress is also an aggravating factor.
NE may occur in various other circumstances, such as upper airway obstruction. ENT surgeons report resolution of NE after children have large adenoids removed, relieving their upper airway obstruction.
Constipation may cause secondary NE or may cause primary NE to persist. One of the reasons may be due to the loaded rectum and sigmoid compressing the bladder and reducing storage capacity. Constipation should be sought and actively treated in every child with NE.
Polyuria in diabetes mellitus and insipidus increases the risk for NE, mostly of the secondary type. Children with minor neurological dysfunction are also more vulnerable to NE. And children with ADHD are 2.7 times more likely to have NE than the general paediatric population.
A detailed history is important for identifying PMNE. If there is no history of pronounced urgency, frequency, or infrequent voidings, and in particular no daytime wetting, then a diagnosis of PMNE can be made.
Other points to be noted are: the family history, whether the child is a deep sleeper, fluid intake and voiding habits, and snoring (which may point to enlarged tonsils and adenoids). Children around 7 years of age with normal bladder function should pass urine 5-7 times a day, with a fluid intake of about 1.2 litres spread evenly throughout the day.
Medication for ADHD may also affect NE. Details about bowel habits, and intake of bladder irritants such as blackcurrant juices, fizzy drinks, and caffeinated drinks should also be sought.
If there are symptoms of bladder dysfunction, a voiding diary and non-invasive urodynamic assessment are necessary, with urinalysis to provide a baseline.
Addressing significant daytime symptoms can help with the resolution of NE.
Bladder capacity for children up to the age of 11 is calculated using the formula ‘age + 1 x 30’, so a child aged 7 years should have a bladder capacity of around 240 ml. At this age the overnight production of urine is about 200 ml, well below the normal bladder capacity.
In England, treatment for PMNE is not usually started until about 7 years of age. The management is based on the underlying aetiology. It is important to warn parents and the child that treatment may be prolonged – there is no quick fix.
The child should be told at their first visit that NE is common. Reassurance is important, because in most children NE resolves spontaneously or with the help of interventions. At the age of 16 years only 1% of children will still wet the bed.
It is important to determine how motivated the child is for treatment, and to exclude psychosocial factors.
It has been recognised that in children above age 10, NE may itself cause psychological problems and difficulties with social adjustment. This is a strong indication to intervene as soon as the child is ready to receive treatment.
An assessment of the psychological impact of NE includes asking about teasing and avoidance of sleepovers or school trips. The child’s verbal and body language responses to these questions should be observed.
If the child does not appear concerned, it is likely they will not be bothered about the enuresis either, and so may not be motivated to undergo treatment. An adequate fluid intake evenly spaced out during the day is important, and regular voiding should be encouraged. Fluid intake should be stopped after the evening meal. Bladder irritants should be avoided.
Bed alarms or alarms worn on the body are effective in NE, with a lasting cure in about 40% of cases after 6-8 weeks. At first, the alarm may wake the rest of the family rather than the child, causing stress. Bed alarms are available either from the local continence centre or online.
Nocturnal polyuria can benefit from treatment with the antidiuretic drug desmopressin. Used alone it can have a success rate of 60%, but there is a high relapse rate after short-term use. It can be prescribed as sublingual tablets which dissolve without the need for a drink of water.
A starting dose of 120 micrograms should be prescribed, and increased to 240 micrograms if there is no effect after a few weeks. Desmomelts are more effective than Desmotabs. If there is a good response, Desmomelts can be continued for two months at a time, with a two-week drug-free period in between. Alternatively some families prefer to use them for specific occasions such as holidays and sleepovers.
A combination of desmopressin and a bed alarm is synergistic and may have most success. If there are symptoms of overactivity of the detrusor, an anticholinergic such as oxybutynin can be prescribed. Imipramine may be used as a third-line medication for NE where all other factors contributing to NE have been ruled out or treated.